Process for preparing fibers of the polyester series having different dyeability

ABSTRACT

PROCESS FOR PREPARING FIBERS OF THE POLYESTER SERIES HAVING DIFFERENT DYEABILITY, CHARACTERIZED BY SUBJECTING FIBERS OF THE POLYESTER SERIES TO A NON-CONTACT HEAT TREATMENT MOMENTARILY UNDER VERY LOW TENSION IN THE ATMOSPHERE KEPT AT A TEMPERATURE ABOVE THE MELTING POINT OF SAID FIBERS, WHEREBY REMARKABLE DIFFERENT DYEABILITY IS IMPARTED TO THE FIBERS ALONG THE FIBER LENGTH DIRECTION.

Jan. 11, 1972 HIDEQ w sE ETAL 3,634,580

PROCESS FOR PREPARING FIBERS OF THE POLYESTER SERIES HAVING DIFFERENTDYEABILITY Filed Feb. 4, 1969 Fig.3

United States Patent Office 3,634,580 Patented Jan. 11, 1972 US. Cl.264-342 1 Claim ABSTRACT OF THE DISCLOSURE Process for preparing fibersof the polyester series having different dyeability, characterized bysubjecting fibers of the polyester series to a non-contact heattreatment momentarily under very low tension in the atmosphere kept at atemperature above the melting point of said fibers, whereby remarkabledifferent dyeability is imparted to the fibers along the fiber lengthdirection.

The present invention relates to a process for preparing fibers of thepolyester series having different dyeability. More particularly, thepresent invention relates to a process for preparing fibers of thepolyester series having remarkable dyeing differences along a directionof length of the fibers. Heretofore, as a process for preparing fibershaving varying shades of color brought about by dyeing, a process ofunequal drawing after spinning has been known. Portions where a drawratio is low are dyed in a deep color and portions where a draw ratio ishigh are dyed in a thin color. However, when it is attempted to obtainfibers having a large difference in shade, the tenacity of the fiberslowers. Namely, when a portion of a very low draw ratio, for instance,non-drawn portion is put aside and the remaining portion is drawn, thedifference in shade becomes large; however, the mechanical properties ofthe fibers remarkably deteriorate. So far, fibers having practicalmechanical properties and large difference in shade have not beenobtained. Also by such a process it is difficult to obtain fibers havinglarge difference in shade wherein color changing lengths are short; thisbecomes more difficult in fibers prepared continuously at a high speed.

The present invention improves said various deficiencies brought aboutin concomitance with imparting to fibers of the polyester seriesdifferent dyeability through a mass production technique. An objectthereof is to provide fibers of the polyester series having differentdyeability so that when dyed the fibers show a remarkable ditference inshade along a direction of length of the fibers, wherein mechanicalproperties of said fibers are retained on the level of practical use.

Another object of the present invention is to provide fibers of thepolyester series wherein change in shade occur at short intervals, andthe feel of the fiber is improved by development of peculiar crimps insaid fibers of the polyester series having different dyeability.

A further object of the resent invention provides a process forcontinuous mass production at a high speed of fibers of the polyesterseries having the aforementioned remarkable different dyeability as wellas improved feel.

Brief explanation of the accompanying drawings is as follows.

FIG. 1 is an enlarged side elevation of filaments of the polyesterseries having non-periodic different dyeability provided by the processof the present invention. FIG. 2 is an enlarged view of said filamentsof FIG. 1. FIG. 3 is a longitudinal sectional view of a heat treatingapparatus used in the present invention. FIG. 4 is a graph showingrelation of heat treating temperature and dyeability of treated fibers.

It has been found that in order to obtain a sufficient deep color inpolyester fibers, it is necessary that dyeability of the fibers as awhole be improved above a certain standard; moreover, said dyeabilityhas a close relation to the degree of crystallinity of the fibers and itis necessary that the degree of crystallinity of the fibers aftertreatment be at least 40%. It has been found that when fibers of thepolyester series are subjected to a momentary non-contact heat treatmentunder a very low tension in the atmosphere kept at a temperature abovethe melting point of the fibers, different dyeability is brought aboutin the direction of length of the fibers. At the same time, a specialcrimp is brought about in the fibers per se. With regard to the heatingapparatus, the present invention carries out non-contact heating asshown in FIG. 3. In a cylinder 2 a high temperature atmosphere iscreated and fibers of the polyester series are made to pass therethroughunder low tension. The passing time is momentary, e.g. 0.020.10 second.In FIG. 1, many filaments 1 gather and they are loosely intertwined inmulti filamentary state. When said filaments are dyed after beingsubjected to the heat treatment of the present invention, difference ina shade of color is brought about on said filament. In FIG. 1 and FIG. 2a is a deep color portion, while b is a thin color portion. Colorationof a shade of color is in many cases non-periodic. It is possible thatwhen said filaments pass momentarily through a high temperature (abovethe melting point of the filaments) gas, perhaps the filaments are notmelted but they receive sudden heating. That heating is unequal. Forinstance, when there is a stream in a heated gas, when the side surfaceof said filaments directly facing said stream is compared with the sidesurface of said filaments at the rear of said surface, there is adifference in heating. Between outer filaments and inner filamentsconstituting a filamentary yarn, there is naturally great difference inheating. Generally filaments shrink by heating. Said shrinkage varies inproportion to the temperature of heating. In case of filaments, aplurality of monofilaments shrink en masse, however, variation thereofbecomes very complicated. When shrinkage is great, coloration becomesstrong and in portions shrinking little, coloration becomes weak. Asmentioned above, when fibers of the polyester series are momentarilyheated at a temperature above the melting point of said fibers, fibersshrink and as a result shrunken parts are dyed deeply, which is shown inFIG. 4. Namely, FIG. 4 shows the relationship between the heat treatingtemperature C.) (abscissa) and the dyeability (ordinate) in case of heattreating polyethylene terephthalate filaments in high temperature airunder low tension for 0.15 second as an example. The dyeability asherein referred to is determined as follows. Namely, the fibers are dyedin a boiling dye bath of Dispersal fast Scarlet B, 4% O.W.F. for 30minutes, the fibers are dissolved in a solution of orthochlorophenol andthe dyeability is determined from an optical density of 515 m indicatedby a relative value when the dyeability of the non-treated fibers ismade 1. For the foregoing reasons different dyeability develops. Namely,due to sudden heating filaments shrink. Because the heating is unequal,there is unevenness in shrinking. Due to this unequal shrinkingso-called different dyeability occurs, because portions shrinking muchare dyed deeply and portions shrinking little are dyed weakly. Also inthe present invention there is development of peculiar crimp, which iscaused by shrinking of the filaments at the time of heat treatment.

Next, concerning different dyeability of fibers of the polyester seriesdue to heat treatment, when the cause therefor is considered and studiedexperimentally, it is found that in development of different dyeabilityvarious conditions participate. When illustrated, they are a high or lowtemperature, a long or short time of heat treatment 4 Upon carrying outa heat treatment, filaments to be treated were passed through a heatingcylinder having an internal diameter of 8 mm. and a length of 30 cm.under tension imposed on said filaments of substantially zero.

and tensile strength imposed on the filaments. These vari- 5 In Table 1,in Nos. 114, the filaments treated Were ous elements do not work alonebut have intimate correnormally drawn and heat-set polyethyleneterephthalate lationship. At first unequal shrinking of the filamentscausyarn (75 de./ 36 fil., inherent viscosit in o-chlorophenol ingdevelopment of different dyeability is made one target at 35 C. of 0.62,draw ratio: 3.65, heat-set temperature: and what roles these variouselements play thereto will 170 C., shrinking in boiling water: 6%,degree of crystalbe considered. 10 linity: 47% whereas in Nos. -19', thefilaments treated As a temperature, a fluid temperature in the heattreatwere non-heat-set polyethylene terephthalate yarn (denier, ing zoneis considered, which temperature is above the inherent viscosity anddraw ratio were same as in the melting point of fibers of the polyesterseries, preferably a cases of 'Nos. 1-14, shrinkage in boiling water:12%, temperature higher than said melting point by at least degree ofcrystallinity: 25%). In Table 1, (1) degree of 100 C. is adopted. Whenthe melting point is 270 C., 15 shade was: (O)-remarkable, (A)fairlygood, and the fluid temperature for heating is preferably at least(X)-no difference in shade recognized. 370 C. As the highesttemperature, more than l,000 C. (2) Degree of crystallinity wasdetermined by an X-ray may be conceived. Difference in shade isremarkable when diffraction method, whereby the fiber axis was placedperthe treating temperature is higher; difference in shade ispendicularly to an X-ray beam, an X-ray diffraction curve difficult tosee when the treating temperature becomes low in a direction at a rightangle with the fiber axis was measand when the temperature is below themelting point of ured and said degree could be simply determined by thethe filaments, different dyeability is completely not recogfollowingmethod. Namely, on both sides (a lower angle nized. However, it shouldbe noted that other elements are side and a higher angle side) of a peakof Xray diffraction also important. Next problem is the treating time;the pattern in the vicinity of 175 C. in said X-ray diffraction time isdetermined from a velocity at which the filaments curve, a line wasdepicted so as to contact an intensity of to be treated pass through theheating zone and the passing X-ray diffraction peak curve. From thehighest point A length. Generally, when the heat treating time is too ofsaid peak of X-ray diffraction pattern, AC was depicted short, asufficient effect of heat treatment cannot be obperpendicularly to saidaxis. AC showed an intensity of tained and it is not possible to achievethe objects of the X-ray diffraction pattern at the point A, anintersecting present invention. The heat treating effect varies mainlypoint of AC with the previously depicted tangent was by the heattreating temperature and time, and because made B and degree ofcrystallinity was sought from the higher the temperature, the larger theheat treating AB/AC 100%. effect, the time required for obtaining thepredetermined As will be apparent from Table 1, when the treating heattreating effect may be short. Again, in the present temperature was lessthan the melting point of the polyinvention, because the fibers of thepolyester series are ester +l00 C., no difference in shade was obtained(Nos. heat treated at a high temperature above the melting point 1, 2and 3). Namely, even if the degree of crystallinity of said fibers, Whenthe heat treating time is too long, the of the filaments was more thanwhen the treating fibers melt completely. Because of this, the longestheat temperature was low, different dyeability could not the treatingtime has a limit of itself, about which mention 40 obtained.

will be made in detail later. Finally, there is a problem of tensilestrength of the filaments, which is preferably very weak. It ispreferable to enable the filaments shrinking by heating to freely modifyand this modification should not be restricted.

In the foregoing, the heat treating temperature is made T C.), themelting point of the fibers of the polyester series is made Tm C.) andthe heat treating time is made 1 (sec.) and relation existing among themis determined.

It is perhaps impossible to theoretically analyze the present inventionand the relationships involved are determined mainly based on theresults obtained experimental- 1y. In Table 1, results of practicing theprocess of the present invention are shown.

By arrangement of the experimental results described above, Table 1 andother data, the primary variables T: heat treating temperature C.

Tm: melting point of polyester C. t: treating time, see. were plotted ona sheet of logarithmic section paper to obtain empirical Formulas 1 and2.

log Tlog Tm==0.688-0.588 log t (1) and the treating temperature isnecessarily not less than t defined by said Equation 1, and its upperlimit is:

log (T--Tm)'=1.576--1.0851og t (2) Namely, the treating temperature isnecessarily not more than t calculated by said equation 2. The reason T,Tm

TABLE 1 1th- C ystal- Degree Shrinklyeatlug Forwarding drawing Treatinglinity of a age in temp,. velocity velocity time, degree, shade boilingNumber C. m./min. mJmin. sec. percent of color water Remarks 250 90 0.24 53 X 0. 5 Comparative example. 300 75 0. 24 58 X 0. 4 Do. 300 1740.12 53 X 1.0 Do. 360 00 75 0. 24 60 0 0. 4 D0. 360 174 150 0. 12 57 A0.8 360 351 300 0.06 52 A 2.0 400 174 150 0. 12 60 0 0. 1 400 351 300 0.06 55 0 1.0 400 545 450 0 04 51 A 2. 8 400 608 600 0. 03 48 X 1. 0 Do500 545 450 0. 04 59 0 0. 2 500 608 600 0. 03 52 A 1. 0 500 062 900 0.02 40 X 4. 5 1000 825 750 0. 24 55 0 0. 5 400 284 225 0. 08 56 0 0. 5400 545 450 0. O4 42 0 2. 7 400 608 600 0.03 35 X 4. 5 Do. 500 (508 6000.03 15 0 l. 0 Do. 500 825 750 0. 024 40 A l. 0

and t are arranged as mentioned above is, even if it is calledunconditionally high temperature heat treatment, its varying scope(combination of T with t) is very broad, and there is a scope wheredifferent dyeability is not developed. For example, in said Equation 2,when t is made too large, it exceeds the upper limit, resulting ininconvenience. Namely, not only different dyeability is not developed,but also actually the filaments melt, inviting an entirely differentresult. On the contrary, as examples of making small t, in cases of Nos.10, 13 and 18 the treating temperatures in said Equation 1 are withinthe range of the present invention, however, because the treating timesare made less than t, it is understood that the objects are not achievedsimilarly.

When the description made so far is summarized, construction of thepresent invention is as follows.

(1) Fibers of the polyester series are made to pass through a hightemperature atmosphere kept at a temperature higher than the meltingpoint of said fibers.

(2) In the above case, fibers transfer under low tension (e.g less than0.03 g./de.)

(3) Relation among T, Tm and t is according to the following empiricalequation.

log T-log Tm =0.688-0.588 log t (4) The final degree of crystallinity ofthe fibers after treatment is at least 40%.

In the present invention, upon carrying out a high temperature heattreatment, as the medium for heating the fibers, a gas is most suitable.Namely, a gas heated to the desired temperature is filled in thecylinder 2 shown in FIG. 3. For keeping the temperature constant a gasat a predetermined temperature may be supplied from an entrance 4 at oneend and discharged from an exit 5 at the other end or the filaments maybe passed through an electricially heated chamber.

As another kind of a heating apparatus, means of irradiating infraredray to the filaments may be adopted. A heating apparatus of an optionaltype other than what is illustrated may be adopted. The heat treatingtemperature as herein referred to is a temperature of a heating mediumin the vicinity of the surface of the fibers to be treated, which can beeasily measured by, for instance, a thermocouple.

The fibers of the polyester series usable in the present invention arehomopolyester or copolyester all or a main part of an acid component ofwhich is terephthalic acid and all or a main part of a glycol componentof which is ethylene glycol. A blend which is spun by the conventionalprocess and further subjected to drawing or drawing followed by heat-settreatment is preferable, especially a multifilament yarn is mostsuitable.

When the filaments heat treated by the aforementioned process of thepresent invention and dilferent dyeability state are observed,non-periodic as it is, a very clear shade of color is shown, thechanging scope of the color tone is very short and it is possible toobtain a scope of several centimeters or even several millimeters. Thefact that the filaments have such complicated different dyeability asmentioned above is very useful depending upon the desired use. Dependingupon a dyeing method, for instance, in case of a print, it is possibleto make almost invisible different dyeability and the dyed fibers may beolfered for use wherein feel only is estimated.

Because the process of the present invention carries out a non-contactheat treatment, it is possible to treat the fibers continuously at ahigher speed.

The fibers treated by the process of the present invention retainpractical mechanical properties.

The fibers treated by the process of the present invention are impartedwith different dyeability remarkable in distinction of a shade of color.

The fibers treated by the process of the present invention developpeculiar crimp, having special feel.

6 EXAMPLE 1 Non-heat-set drawn polyethylene terephthalate filaments (75de./36 fil, an inherent viscosity measured in o-chlorophenol at 35 C. of0.61, An:=0.141) were passed through a cylindrical tube having adiameter of 1.9 cm. and a length of 30 cm. heated by electric heat to550 C. and continuously heat treated in heated air at a withdrawingspeed of 30 m./min. under tension of 0.0 g./de. (in the followingexample the same apparatus was used). The treated filaments obtainedwere finely crimped and by dyeing (dyeing for 30 minutes using Dispersalfast Scarlet B, dyeing in the following example was same as this), ashade of color at a cycle of about 2 cm. was brought about on saidfilaments. Filaments heat treated under conditions same as above excepttension was changed to 0.04 g./de. exhibited no crimp, and when thefilaments were dyed no periodic shade of color was recognized.

EXAMPLE 2 A polyethylene terephthalate yarn having a Y-shaped crosssection (50 de./48 fil.) was heat treated at 500 C. under tension of0.01 g./de. and a withdrawing speed of 300 m./min. As a result of dyeingsaid yarn, a fine and remarkable shade of color having a cycle of about5 mm. was brought about.

EXAMPLE. 3

Heat-set filaments of polyethylene terephthalate having copolymerized 5%by weight of polyethylene glycol (melting point: 258 C., 50 de./24 fil.,inherent viscosity: 0.62, An =0.148, shrinkage in boiling water: 7.8%,shrinkage at dry heat of 150 C.: 9.5%) were heat treated at 500 C. undersubstantially no tension at a with drawing speed from a heated zone of300 m./min. As a result, filaments exhibiting a shade of color at acycle of about 2 cm. were obtained. The shrinkage in boiling water ofsaid treated fibers was 2.5% and shrinkage at dry heat of 150 C. was3.0%.

EXAMPLE 4 Polyethylene terephthalate filamentary yarn processed by afalse twist method was heat treated at 550 C. under tension ofsubstantially Zero at a withdrawing speed of 300 m./min. As a resultyarn having a difference in shade in a direction of length of about15-20 cm. was obtained.

EXAMPLE 5 Drawn heat-set polyethylene terephthalate filaments (75 de./36 fil., inherent viscosity in o-chlorophenol at 35 C. of 0.6, An=0.161)were passed through a dry heated cylinder having an internal diameter of8 mm. and a length of 30 cm. and continuously heat treated at 600 C.under tension of 0.005 g./de. at a withdrawing speed of 600 In./min. Theso obtained filaments were finely crimped, and when dyed exhibited aremarkable shade of color at a cycle of about 2-3 cm.

The shrinkage in boiling water of said treated filaments was 0.4% andshrinkage at a dry heat of 150 C. 'was 0.5%.

What is claimed is:

1. A process for preparing a continuous multifilament yarn of a linearpolyester, the filamentary yarn of which consists of deep-dyeing portionand pale-dyeing portion occurring alternatively along the axis of thesaid yarn, which process comprises passing a drawn polyestermultifilament yarn through a high temperature stationary atmospheremaintained at a temperature (T) at least C. higher than the meltingpoint (Tm) of said polyester up to about 1000 C., for a period of time(t) of 0.02 to 0.24 second, under a yarn tension of less than 0.03

7 8 gram per denier so that the final degree of crystallinity 3,156,75211/1964 Cope 264-342 R is at least 40%, the variables T, Tm and t,satisfying 3,166,886 1/ 1965 Kretsch 28- 72 the equations 3,443,0095/1969 Chirgwin 2861 3,022,564 2/1962 Price 2855.2 0-588 log t 53,367,003 2/1968 Scott R 10g s I 3,421,194 1/1969 Breen et a1. 28--72.123,490,219 1/1970 Ozawa et a1. 57-34 References Cited UNITED STATESPATENTS JAY H. WOO, Primary Examiner 2,956,330 10/1960 Potzl 264-342R 103,005,251 10/1961 Hallden et a1 2876 US 3,011,215 12/1961 Alley 264 210L 814, 15, 149.3; 2862; 264235, 346

3,069,836 12/1962 Dahlstrom et a1. 264342 R

